IMPROVED PHOSPHORIC–NITRIC ACID DIGESTION METHOD FOR ACCURATE DETERMINATION OF TUNGSTEN IN SOIL MATRICES

Accurate determination of tungsten in soil matrices is essential for understanding its environmental behavior and mobility. Conventional acid digestion procedures often result in low tungsten recovery due to the formation of insoluble species under acidic conditions. This study evaluates a modified phosphoric–nitric acid digestion method designed to enhance tungsten solubilization through the formation of stable phosphotungstate complexes. The modified procedure was compared with standard nitric and nitric–hydrochloric acid methods using reference materials and test soils. Results demonstrate significantly improved recovery efficiency and acceptable matrix spike performance. The method also allows simultaneous determination of other metals, ensuring analytical reliability and broader environmental applicability.